Levulinic acid esters (LAEs) were synthesised from -angelica lactone and alcohols, in a reaction catalysed by a new family of chloride-free Lewis acidic ionic liquids, containing trifloaluminate anions, [Al(OTf)3+n] n-. Changing the catalyst from poorly soluble Al(OTf)3 (used as suspension) to fully homogenous trifloaluminate ionic liquids resulted in shorter reaction times required for full α-AL conversion (60 min at 60 °C for 0.1 mol% catalyst loading), and unprecedented selectivities to LAEs, reaching >99%. Supporting the trifloaluminate ionic liquid on multi-walled carbon nanotubes gave an easily-recyclable system, with no leaching observed over 6 cycles. Mechanistic considerations suggest that the propensity of Al(OTf)3 to undergo very slow hydrolysis results in the correct balance of Brønsted and Lewis acidic sites in the system, inhibiting by-product formation.

Dicationic and tricationic ionic liquids, synthesised by proton trasfer from sulfuric acid and corresponding di- and triamines, were characterised and used as Brønsted acidic catalysts in the biodiesel production. It...

Continuous flow chemo-enzymatic Baeyer−Villiger oxidation in the presence of exceptionally active Candida antarctica lipase B immobilized via simple physical adsorption on multiwalled carbon nanotubes has been investigated. The nanobiocatalyst was used to generate peracid in situ from ethyl acetate and 30 wt % aq. hydrogen peroxide as the primary oxidant. Application of the highly stable and active nanobiocatalyst in the Baeyer−Villiger oxidation of 2-methylcyclohexanone to 6-methyl-ε-caprolactone after 8 h at 40 °C led to a high product yield (87%) and selectivity (>99%). Environmentally friendly ethyl acetate was applied as both solvent and the peracid precursor. To determine the most favorable reaction conditions, a series of experiments using various parameters was performed. The main contribution of this work is that it describes the first application of the nanobiocatalyst in a chemo-enzymatic Baeyer−Villiger oxidation in a flow system. Since the process was performed in a flow reactor, many improvements were achieved. First of all, substantially shorter reaction times as well as a significant increase in the product yield were obtained as compared to the batch process. Since peracids are unstable, a large increase in the safety of the process was demonstrated under mild conditions in this work. In summary, this work shows a particularly efficient upgrade in the studied processes by transfer from a batch to a flow system.

This study presents a highly efficient method of a synthesis of n-butyl acrylate via esterification of acrylic acid and n-butanol in the presence of supported ionic liquid phase (SILP) biocatalyst consisting of the lipase B from Candida antarctica (CALB) and multi-walled carbon nanotubes (MWCNTs) modified by D-glucose-based ionic liquids. Favorable reaction conditions (acrylic acid: n-butanol molar ratio 1:2, cyclohexane as a solvent, biocatalyst 0.150 g per 1 mmol of acrylic acid, temperature 25 °C) allowed the achievement of a 99% yield of n-butyl acrylate in 24 h. Screening of various ionic liquids showed that the most promising result was obtained if N-(6-deoxy-1-O-methoxy-α-D-glucopyranosyl)-N,N,N-trimethylammonium bis-(trifluoromethylsulfonyl)imide ([N(CH3)3GlcOCH3][N(Tf)2]) was selected in order to modify the outer surface of MWCNTs. The final SILP biocatalyst–CNTs-[N(CH3)3GlcOCH3][N(Tf)2]-CALB contained 1.8 wt.% of IL and 4.2 wt.% of CALB. Application of the SILP biocatalyst led to the enhanced activity of CALB in comparison with the biocatalyst prepared via physical adsorption of CALB onto MWCNTs (CNTs-CALB), as well as with commercially available Novozyme 435. Thus, the crucial role of IL in the stabilization of biocatalysts was clearly demonstrated. In addition, a significant stability of the developed biocatalytic system was confirmed (three runs with a yield of ester over 90%).

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Stability studies dedicated to high-energy compounds for a series of linear peracids (C6–C12), including sensitivity to mechanical impulse, electrical and thermal sensitivity, were presented in this work for the first time.

A highly active biocatalyst based on a hybrid platform was designed for the conversion of α-angelica lactone to alkyl levulinates.

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